The instant application is based upon French Patent Application No. 99 13965, filed Nov. 2, 1999, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. xc2xa7119.
1. Field of the Invention
The present invention relates to a wheel primarily for a roller skate, especially for a skate whose wheels are aligned.
2. Description of Background and Relevant Information
Skate wheels are generally constituted of a hub made of a very rigid plastic material, such as polyamide, for example, on which a tread, made of one or several materials having a lower modulus of traction than that of the hub, such as polyurethane, for example, is duplicate, molded.
The characteristics which a good wheel must have are numerous. Initially, the tread must have good adherence qualities, which is particularly true for the portions thereof that are in contact with the ground in curves, i;e., when the wheel is inclined. The tread adherence depends mainly on the properties of its constituent material, i.e., on its chemical constitution, and on its macro-molecular properties.
Second, the wheel should not be overly flexible. Indeed, too much flexibility in the wheel causes a substantial deformation thereof, which negatively. affects performance, especially in terms of speed and stability.
Third, the wheel must be as resilient as possible. The resiliency of a wheel is translated into its capacity to return the maximum of the energy that is transmitted to it. This is easily appreciated by the rebounding effect of the wheel. A highly resilient wheel therefore promotes speed, because it is capable of returning a substantial portion of the energy during the expansion that follows the compression of the wheel. A non-resilient wheel absorbs much of this energy and dissipates it as heat.
Fourth, an in-line roller skate wheel must be such that the hub should not come in contact with the ground at any time during use. Indeed, in a curve and at very high speed, i.e., when the wheel is very inclined, the zone of the hub that interfaces with the tread, i.e., the peripheral zone of the hub, runs the risk of coming in contact with the ground. As a result, there is an automatic, definitive. loss of adherence.
Fifth the wheel, axle and frame assembly must be stable and should not permit any deformation, especially when the wheel is biased along a direction that is not in its median plane.
Finally, a wheel must be lightweight, and especially inexpensive to manufacture.
The document WO 96/20030 proposes to construct a skate wheel in which the lateral zones of the tread are not as hard as the central zone. Such a wheel remains heavy and especially very expensive to make.
Another document, U.S. Pat. No. 5,924,705, proposes to modify the deformability of the lateral zones of the tread by providing annular grooves on the sides thereof. Depending on the dimensions of the grooves, the use of such a wheel generates a weight gain. However, such a solution is not applicable to all wheel-profiles. Indeed, to avoid a substantial modification of the wheel behavior in curves, these annular grooves located in the tread cannot open up in a zone that comes in contact with the ground when the wheel is inclined. This is one of the reasons why a particular wheel profile was selected in this document, namely, a wheel having a substantially flat tread surface framed by substantially vertical flanks. This particular profile provides a relatively large contact surface in a straight line, which limits speed performance.
In another embodiment described in this same document, a skate wheel is provided whose rigidity can be modified by adding disks in cavities that have been especially adapted to receive them. The disks are removable and fixed on the hub by means of screws. The choice of versatility in this embodiment has led the designer to envision only one particular form of cavity, namely, a shallow cavity. Indeed, it is necessary to ensure that the residual width of the hub, in the area of the cavities, is sufficiently large to enable the positioning of the means for fixing the disks. Furthermore, such a wheel is not economical to manufacture because it requires assembling various parts, especially with screws.
The patent U.S. Pat. No. 5,938,214 proposes to reduce the lateral inclination angle of the frame/wheel assembly. To this end, two solutions are proposed.
In the first solution, an enlarged tread is duplicate molded on a conventional hub, i.e., a hub whose width enables the arrangement of two bearings and a spacer. Such an arrangement makes it possible to reduce the lateral inclination angle of the frame/wheel subassembly.
Furthermore, due to such an arrangement, the risk of contact of the hub with the ground is practically avoided. However, the necessity to enlarge the tread causes an increase in the weight of the wheels, and therefore of the skate, which is contrary to a search for performance. Moreover, such a wheel requires a specific frame, i.e., a frame including several independent pairs of wings serving to fix the axles of the wheels. The stability of the frame is reduced due to the independence of the four pairs of wings.
The second solution uses a tread having a conventional profile that is fixed to a hub that has only one bearing. In this solution, the weight gain occurs at the expense of the holding stability of the wheel on its axle.
The document U.S. Pat. No. 5,655,784 describes a skate wheel provided to be fixed on an axle by means of a single bearing, and which is equipped with a tire whose width is reduced with respect to that of the hub. Furthermore, the hardness of the material used for the tire is higher than 85 durometers on the A scale. In fact, it is comprised between 60 and 85 durometers on the D scale. Such a hardness provides the wheel with a very low resiliency and only offers very little adherence to the user of this wheel. Furthermore, the presence of a single bearing requires the use of a bearing having a very large outer diameter, and does not offer an optimum stability to the skate, especially when the latter is biased along a direction that is not in the longitudinal plane of the skate.
The standard wheels that are commonly used on the in-line roller skates have a hub about 24 millimeters (mm) wide, and whose outer diameter varies generally between 38 and 45 mm. This is a diameter that does not take into account the interlock that is embedded in the tread. This value is to be applied to the total outer diameter of a wheel that varies approximately between 72 mm and 82 mm. Indeed, it is estimated that to eliminate the risk of contact of the hub with the ground, the outer diameter of the hub should not exceed 60% of the value of the total outer diameter of the wheel, and preferably should not exceed 55%. The wheels that have a hub larger than 45 mm and whose diameter does not exceed 82 mm put the user at a great risk of hub/ground contact.
Furthermore, the standard wheels are mounted on an axle by means of two roller bearings whose diameter is less than or equal to 22 millimeters. The two bearings are arranged at a distance from one another at both ends of the inner surface of the hub.
For economical reasons, the manufacture of the largest portion of the skate wheels calls for the techniques of duplicate molding of plastic materials. The hub is first obtained by plastic molding or injection; the tread is then duplicate molded. Gravity molding along a feed bush is then used. After demolding, a sprue remains, which is located on one of the flanks of the wheel, in the area of the hub/tread interface. This sprue is then cut along a direction perpendicular to the axle of the wheel. Manufacturing the skate wheels by duplicate molding makes it possible to produce wheels that have satisfactory performances at low cost. However, it does not make it possible to obtain wheels having a particular profile, especially because of the cutting of the sprue that is perpendicular to the axle of the wheel.
An object of the present invention is to overcome the aforementioned disadvantages. This means designing a wheel that benefits from a very good adherence, even when substantially inclined, and which enables a weight gain.
This also means designing a wheel which, even when it is used in standard configurations, allows for an increase in the outer diameter of the hub, in the sense defined hereinabove. The present invention also includes a method of manufacturing that makes it possible to obtain such a wheel.
To resolve the problem posed, a wheel is provided, which includes: a generally annular tread having an axis of rotation OOxe2x80x2; a generally annular hub having an axis of rotation OOxe2x80x2 including an interface zone ensuring the cohesion of the hub and of the tread, a substantially cylindrical central surface adapted to cooperate with a mechanism for fixing the wheel on a rotation shaft having an axis OOxe2x80x2, and a hub body connecting the central surface to the interface zone; an annular groove having an axis of rotation OOxe2x80x2, limited radially on one side by the hub body, and on the other side, at least partially, by the tread; the groove having a profile that is substantially triangular, trapezoidal, semi-circular or a shape combining portions of the three preceding profiles.
Since the annular groove is not provided only in the tread or in the hub, but in both at the same time, one can therefore increase the volume recessed by the groove and thus obtain a more substantial weight gain in comparison to the wheels known from the state of the art. Moreover, due to its smaller width, the hub/tread interface surface no longer runs the risk of coming in contact with the ground when the wheel is inclined. Furthermore, for a given wheel diameter, a hub having a larger diameter can be used. In view of the differences in density and rigidity between the materials that are commonly used for the hub and the tread, a weight gain approximating 20% can be obtained due to the wheel according to the invention.
The bottom of the annular groove, i.e., the assembly of the deepest points, is a circle whose center is located on the axis OOxe2x80x2. The latter is located on the: lateral surface of the hub, at a distance from the hub/tread interface surface. In a preferred embodiment of the invention, the depth of the groove is at least greater than 20% of its width. Advantageously, an annular groove is provided on each of the flanks, these two grooves having a symmetrical position relative to one another with respect to the median plane of the wheel. The bottom of these two annular grooves corresponds to the area where the width of the hub is the smallest. Preferably, this smallest width Lm of the hub is less than the width of the tread in the area of the tread/hub interface, also called the width Lsi of the interface surface.
Preferably, the tread includes a material whose hardness is comprised between about 60 and about 90 Shore A.
Preferably, the central limit of the annular groove is located in the vicinity of the central surface of the hub. In other words, it is said that radially, the annular groove begins in the vicinity of the central surface of the hub.
The peripheral limit of the groove is located on the tread. In a preferred embodiment, this peripheral limit corresponds with the central limit of the surface of the tread that is capable of coming in contact with the ground. Preferably, this peripheral limit is positioned such that the difference between the radius of the wheel and the radius of the peripheral limit of the groove is substantially equal to half the width of the wheel, when taken in the area of the tread.
Advantageously, the hub body is not solid, but bored by cavities that may or may not be through cavities. For reasons of simplicity, the surface constituting the lateral outer contour of the hub will continue to be referred to as lateral surface of the hub in the rest of the disclosure and in the claims, i.e., regardless as to whether or not cavities are provided in the hub body.
Since the groove is limited radially, on one side by the hub and on the other side by the tread, the surface of the groove includes a central portion constituting a portion of the lateral surface of the hub body, and a peripheral portion constituting a portion of the outer surface of the tread. As for the lateral surface of the hub, whether or not the latter is bored by cavities, one will refer to a central portion of the surface of the groove. The central portion of the wall of the groove as well as its peripheral portion can have different profiles. However, the peripheral portion will preferably be given the profile of a straight portion, whereas the central portion will have a curved profile
To resolve the problem posed, one also provides a roller skate wheel constituted of a tread and a hub, the hub including an interface zone ensuring the cohesion of the hub and of the tread, a substantially cylindrical central surface adapted to cooperate with means fixing the wheel on a rotation shaft Hand a hub body connecting the inner surface to the interface surface, the interface zone including a substantially cylindrical interface surface on which the tread rests, the width of the interface surface is smaller, than 90% of the width of the central surface. In a preferred embodiment, the interface surface has a width smaller than 80% of the width of the central surface.
Preferably, the material of the tread is a polyurethane elastomer defined by the following intrinsic characteristics: an elastic modulus Exe2x80x3 comprised between about 6 and about 11.3, and a viscous modulus Exe2x80x3 lower than about 0.25. Furthermore, for reasons of comfort, it is preferable to use materials whose hardness does not exceed about 85 shore A to manufacture the tread. To prevent early wear and tear and to maintain a good resiliency in the wheel, one selects materials whose hardness is greater than about 60 Shore A.
The invention also provides for a skate wheel that includes a generally annular hub including an axis of rotation and a substantially cylindrical central surface adapted to cooperate with a mechanism for fixing the wheel on a shaft. The hub includes a first material. A generally annular tread is mounted to the hub and has at least one outer surface adapted to contact a ground surface. The tread includes a second material which is different from the first material and whose hardness is between about 60 and about 85 Shore A. A connecting interface zone is defined between the hub and the tread. At least one annular groove has an axis which corresponds to the axis of rotation of the hub. The at least one groove is arranged on at least one side of the skate wheel in the area of the connecting interface zone. The connecting interface zone includes an interface surface on which the tread rests. A width of the interface surface is smaller than a maximum width of the tread. In the interface zone, a peripheral portion of the tread and a peripheral portion of the hub are tangent to one another.
Moreover, to make a wheel according to the invention, a method is provided, which includes the following: obtaining the hub by molding, injection, gravity casting, extrusion, stamping, forging or diecasting; arranging the hub in a lower mold, whose shape corresponds exactly to the final shape which one wishes to impart to a first half of the tread; closing the mold by positioning an upper mold 21, whose shape corresponds essentially to the final shape which one wishes to impart to the second half of the tread, minus the zone(s) corresponding to the sprue(s), the parting line being perpendicular to the axis of the wheel to be manufactured; gravity casting of the material of the tread by way of a feed bush; the method further including: cutting the sprue along at least one direction that is not parallel to the parting line.
The cutting of the sprue, which is not parallel to the parting line, makes it possible to manufacture, using the gravity casting method, wheels that have a complex profile.
The invention therefore provides for a skate wheel comprising a generally annular hub including an axis of rotation and a substantially cylindrical central surface adapted to cooperate with a mechanism for fixing the wheel on a shaft, the hub including a first material, a generally annular tread mounted to the hub and having at least one outer surface adapted to contact a ground surface, the tread including a second material which is different from the first material and whose hardness is comprised between about 60 and about 85 Shore A, a connecting interface zone being defined between the hub and the tread, at least one annular groove having an axis which corresponds to the axis of rotation of the hub, the at least one groove being arranged on at least one side of the skate wheel in the area of the connecting interface zone, and the at least one groove having a profile, wherein the profile of the at least one groove comprises a shape which is one of substantially triangular, substantially trapezoidal, substantially semi-circular, and combines portions which are substantially triangular, substantially trapezoidal, and substantially semi-circular.
The interface zone may include an interface surface on which the tread rests, and a width of the interface surface may be smaller than about 80% of a width of the cylindrical central surface, and the hub may have a width in the area of the groove which is smaller than the width of the interface surface. The tread may be duplicate molded on the hub. The hub may be made of a single piece. The hub may comprise a plurality of cavities. Each of the cavities may extend through the hub from one side to another side. The profile may extend from the hub to the outer surface of the tread. The profile may include a straight portion arranged on the tread and a curved portion arranged on the hub. A depth of the at least one groove may be greater than or equal to about 20% of a width of the at least one groove. A depth of the at least one groove may be greater than about 15% of a width of the cylindrical central surface. The profile in the area of the tread may comprise a straight portion. The profile may comprise a curved portion. The profile may comprise at least a partially circular portion. A bottom of the at least one groove may be circular. A bottom of the groove may be circular and may be arranged on the outer surface of the tread. The interface zone may include a substantially cylindrical interface surface and an interlock having a substantially annular general shape arranged radially away from the cylindrical interface surface. A width of the interlock may be greater than about 40% of a width of the cylindrical interface surface. The mechanism for fixing the skate wheel on the shaft may comprise a pair of roller bearings arranged within the cylindrical central surface.
The invention also provides for a method for manufacturing a skate wheel having a hub with a rotation axis and a tread attached to the hub, the method comprising forming the hub via at least one of molding, injection, gravity casting, extrusion, stamping, forging, and diecasting, positioning the hub in a lower mold, the lower mold having a shape which corresponds to half of a desired final shape of the tread, positioning an upper mold on the lower mold, the upper mold having a shape which corresponds essentially to half of a desired final shape of the tread, less at least one zone corresponding to a sprue, a parting line of the tread being perpendicular to the rotation axis of the hub, gravity casting of a material which will form the tread utilizing a feed bush, and removing the sprue.
The removing may comprise cutting the sprue via a plurality of cuttings, each of the cuttings occurring along a same direction.
The invention also provides for a skate wheel comprising a hub made of a first material and having a substantially cylindrical central surface adapted to cooperate with a mechanism for fixing the wheel on a shaft, a tread attached to the hub and having at least one outer surface adapted to contact a ground surface, the tread including a second material which is different from the first material and whose hardness is comprised between about 60 and about 85 Shore A, a connecting interface zone being defined between the hub and the tread, at least one annular groove arranged on each side of the connecting interface zone, each of the at least one annular groove having an axis which corresponds to the axis of rotation of the hub and having a profile, wherein the profile of the at least one groove comprises a shape which is one of substantially triangular, substantially trapezoidal, substantially semi-circular, and a combination of portions which are substantially triangular, substantially trapezoidal, and substantially semi-circular.
The invention further contemplates a skate wheel comprising a hub having a substantially cylindrical central surface adapted to cooperate with a mechanism for fixing the wheel on a shaft, a tread attached to the hub and having at least one outer surface adapted to contact a ground surface, a connecting interface zone being defined between the hub and the tread, at least one annular groove arranged on each side of the connecting interface zone, each of the at least one annular groove having an axis which corresponds to the axis of rotation of the hub and having a profile, and a smallest width of the skate wheel being defined between a lowest portion of one groove on one side of the interface zone and a lowest portion of another groove on another side of the interface zone, wherein the smallest width is arranged in the hub.
The invention additionally provides for a skate wheel comprising a hub having a substantially cylindrical central surface adapted to cooperate with a mechanism for fixing the wheel on a shaft, a tread attached to the hub and having at least one outer surface adapted to contact a ground surface, a connecting interface zone being defined between the hub and the tread, at least one annular groove arranged on each side of the connecting interface zone, each of the at least one annular groove having an axis which corresponds to the axis of rotation of the hub and having a profile, and a smallest width of the skate wheel being defined between the cylindrical central surface and the outer surface of the tread, wherein a lower most portion of each groove is at least one of curved, circular, and partially circular.
The invention provides for a skate wheel comprising a hub having a substantially cylindrical central surface adapted to cooperate with a mechanism for fixing the wheel on a shaft, a tread attached to the hub and having at least one outer surface adapted to contact a ground surface, a connecting interface zone being defined between the hub and the tread, at least one annular groove arranged on each side of the connecting interface zone, each of the at least one annular groove having an axis which corresponds to the axis of rotation of the hub and having a profile, and a smallest width of the skate wheel being defined between the cylindrical central surface and the outer surface of the tread, a smallest width of the skate wheel being defined between the cylindrical central surface and the outer surface of the tread, wherein a widest portion of the hub, parallel to the rotation axis, is substantially approximately equal to a widest portion of the tread.
The invention also contemplates a skate wheel comprising a hub having a substantially cylindrical central surface adapted to cooperate with at least two bearing devices for fixing the wheel on a shaft, a tread attached to the hub and having at least one outer surface adapted to contact a ground surface, a connecting interface zone being defined between the hub and the tread, at least one annular groove arranged on each side of the connecting interface zone, each of the at least one annular groove having an axis which corresponds to the axis of rotation of the hub and having a profile, and a smallest width of the skate wheel being defined between a lowest portion of one groove on one side of the interface zone and a lowest portion of another groove on another side of the interface zone.
The invention still further contemplates a skate wheel comprising a hub having a substantially cylindrical central surface arranged between two shoulder portions, each shoulder portion being adapted to cooperate with a bearing device for fixing the skate wheel on a shaft, a tread having a curved outer surface and being attached to the hub, an interface zone being defined wherein the hub is attached to the tread, at least one annular groove arranged on each side of the connecting interface zone, each of the annular grooves having an axis which corresponds to the axis of rotation of the hub, and a smallest width of the skate wheel being defined between a surface on one side of the hub and another surface on another side of the hub, wherein each groove comprises a shape which is one of substantially triangular, substantially trapezoidal, substantially semi-circular, and a combination of portions which are substantially triangular, substantially trapezoidal, and substantially semi-circular.